1. Field of the Invention
The present invention relates generally to a long continuous tube, strip or like material having a coating of brazing powders formed along its length. It also provides a method of and an apparatus for manufacturing such long continuous tubes, strips or the like. More specifically, the long continuous tube, strip or like material formed by the extruding process or the rolling process and having a coating of brazing powders formed along its length may be cut into sections of a specific length to meet the requirements for the particular application. For example, the long continuous tube, strip or like material of the present invention may be used as a flattened, perforated tube section of heat exchanger that is usually built from a combination of the flattened, perforated tube sections and corrugated fins.
2. Description of the Prior Art
A conventional heat exchanger is usually built from a combination of flattened, perforated tube sections and corrugated fins. Usually, the corrugated fins are formed from a base of aluminum or aluminum alloy which is clad with a sheet of brazing substances, and the tube is formed from a base of aluminum or aluminum alloy by an extruding process. Immediately following the extruding process, a further coating of zinc may be applied onto the tube by flame spraying so that the tube maybe protected against any corrosion.
In building the conventional heat exchanger from the combination of the flattened, perforated tube sections and the corrugated fins as described above, the sheet of brazing substances is attached to the corrugaged fins by passing them through a rolling process which may yield more defective products. When those materials are to be recycled for reuse, it is disadvantageously difficult because they may contain several different types of substances.
When a coating of zinc has been previously applied by the flame spraying process onto the tube, so that the tube may be protected against any corrosion, the products yielded through the flame spraying process may disadvantageously contain more defects. It is also noted that zinc solid powders may disadvantageously be produced during the flame spraying process, which may adversely affect the ambient working environment. Any scraps that may be produced from the finished tubes contain the zinc which was coated in the application process. The tube may be placed under the heat produced during the flame spraying process, which may contribute to the growth of oxide film which may adversely affect the efficiency of the brazing process that occurs following the zinc coating process.
In another conventional heat exchanger that has been proposed more recently, a coating of brazing powders that contain silicon powders as a principal component and a certain type of binder as an auxiliary component is applied and formed on the tube, and no sheet of brazing substances is used on the corrugated fins (International publication No. WO92/12821). In this case, it is found that it is difficult to apply a required amount of such brazing powders over the tube uniformly.
The recent trends are toward the multiflow-type heat exchangers in which the tubes become increasingly thinner. It is therefore desirable that a long continuous tube material should be wound up as a coil as it is being finished, and should then be unwound from the coil and cut to specific sections when it is actually used for building a heat exchanger. It is still difficult to apply the uniform coating of the brazing powders, and is thus difficult to obtain uniformly coated tubes.